Slayze

iTrader: (1)

I converted my 10 bolt rear drum over to a 9 bolt disc. I ordered a master cylinder from summit and they have no filter option for rear disc when ordering online. So I decided to call them before ordering and whoever the guy was I was talking to couldn't figure it out either.

So I went ahead and ordered this 36mm one https://m.summitracing.com/parts/dhb-m39576

I will be using that with the wilwood aftermarket proportioning valve. Anyone else might know if I have the right Master cylinder for rear disc?

//<86TA>\\

iTrader: (14)

The factory drum master will work fine, its the proportioning valve that needs to be changed. Or bypassed with a adjustable valve only for the rear brakes

Slayze

iTrader: (1)

Thanks much appreciated happy Thanksgiving to you and yours.

Tibo

iTrader: (15)

Late to the party but if you haven't bought a proportioning valve yet I would steer you toward a unit that accepts both front and rear lines. The adjustable valve is on the rear lines and it splits the front lines internally, keeps a very neat appearance. I'm going to grab one like that in the future as I have the fronts going to a t block and the rear line going to the proportioning valve. Switching is a decision based wholly on aesthetics really.

bigal55

iTrader: (1)

I may be wrong but, I believe a drum brake master cylinder has a check valve so the wheel cylinder(s) cannot retract. If this is used on a disc brake caliper, there will be residual pressure which will keep the brake pads tight against the rotor. Disc brakes are self adjusting in the fact that the pads will only retract enough to not have too much pressure on the rotor. Drum brakes have springs that help to retract the shoes off the drum to release the brakes. Without a check valve, the springs will cause the wheel cylinder to fully retract causing a large clearance between the shoes and the drum, resulting in a long pedal travel. I hope that I explained this clearly and haven't confused anyone. There are different master cylinders for drum versus disc brake apps for this reason. There are other reasons for the difference such as cylinder bore and stroke but the check valve is a major difference. HTH!

JamesC

iTrader: (5)

No need to change. You might check the FAQ about 10-bolt sticky for info about combination valves and masters.

JamesC

bigal55

iTrader: (1)

After searching a little to clarify this, the residual valves were discontinued in the 70s so the third gen shouldn't have this problem. When I converted my 65 chevelle to front disc brakes, I had to find a front disc / rear drum specific master cylinder for proper operation (old school I guess). Sorry if I confused the situation! GL with your conversion!